A traditional bicycle may involve the use of a combination of different sized gears, sprockets, and/or cogs, in combination with a chain oriented thereon, to provide for a range of gearing for a rider. The chain is generally guided to the various gearing combinations by a gear change mechanism, such as one or more derailleurs.
An indication of the state of a gear combination and/or general engagement of the chain may be needed to provide information for an electronic, mechanical, and/or electro-mechanical shift operation of the one or more derailleurs. In a mechanical system a rider may be required to visually identify a gear combination and/or general engagement of the chain by looking at the particular sprockets that are engaged or not engaged. Alternatively, in an electrical and/or electromechanical system the gear combination and/or general engagement of the chain may be inferred or implied based on a measured output or orientation of a motor shaft, or an elapsed time since a shift command was provided to a motor. These techniques may be inconvenient and/or not provide an accurate indication of the actual orientation of the chain due to missed shift actions or other error events that may occur in bicycle transmission systems.